(1) Field of the Invention
This invention relates to a method of biologically controlling a postharvest disease on stone fruit.
(2) Description of the Prior Art
Bacillus subtilis strains have been shown in the past to biologically control various plant diseases in agricultural plants. Some of the examples are as follows:
Thirumalachar and O'Brien showed that a strain of Bacillus subtilis inhibited the growth in vitro of Macrophomina phaseolina and Botryodiplodia solanituberosi, pathogens that cause charcoal rot of potatoes. In field studies, preplant treatment of seedpieces and whole tubers with this bacterial antagonist reduced the frequency of charcoal rot at harvest. (Plant Dis. Reptr., 61:543-546 (1977)).
Utkhede and Rahe undertook a study to identify stable antagonists to isolates of Sclerotium cepivorum for biological control of onion white rot. Significant differences in antagonism were detected among the antagonists. The order of antagonists, ranked according to antagonism and ability to control onion white rot, and depended on the isolate of S. cepivorum being tested. However, the statistical model quantitatively identified useful characteristics in the B2 isolate of B. subtilis. This indicates that the bacterial antagonist B2 has a potential for biological control of onion white rot over a range of isolates of S. cepivorum from five countries. (Phytopathology 73:890-893 (1983)).
Spring wheat seed (Triticum aestivum "Protor") treated with one of several species of the genus Bacillus was planted in hill plots or in pots inoculated with one of six organisms pathogenic to wheat. Yields and root lesion counts were not affected by the seed treatments. (Lengkeek and Otta; Proc. S. D. Acad. Sci., 58:144-156 (1979)).
In a factorialized field trial cells of B. subtilis or phenylmercuric nitrate (PMN) were applied as sprays in autumn to manually defoliated apple trees, C. Bramley's Seedling, artificially infected with Nectria galligena. Trees were additionally sprayed with dithianon at intervals in May and June or left unsprayed at this time. B. subtilis in conjunction with dithianon, and PMN with dithianon were equally effective in the control of canker over a 2-yr period. Dithianon alone gave some control, as did PMN but B. subtilis was not effective without additonal applications of dithianon. (Swinburne and Brown; Ann. Appl. Biol. 82, 365-368 (1976)).
Bacterial colonies are more frequently isolated from leaf scars sampled in December than earlier or later, and among the species present B. subtilis has been found to be highly antagonistic to N. galligena in vitro. Artificial inoculation of leaf scars with B. subtilis immediately after leaf fall reduced the frequency of isolation of all fungal species and reduced the incidence of canker when shoots were inoculated with N. galligena either 24 h after B. subtilis or the following April, but had little effect on their infection with N. galligena in May, when the primary protective layer was found to be shed. More cankers resulted from inoculation in May than in April. The numbers of bacterial colonies recovered from leaf scars inoculated with B. subtilis remained relatively constant from autumn until the primary protective layer was shed the following summer. (Swinburne; Trans. Br. mycol. Soc. 60:389-403 (1973)).
Dunleavy demonstrated that when B. subtilis was added to sterile soil inoculated with Rhizoctonia sp., the incidence of damping-off was reduced considerably in comparison with that which occurred in soil that did not contain the bacteria. (Phytopathology 45:252-258 (1955)).
Microscopic observations of bean leaves treated with B. subtilis showed urediospore germination was greatly reduced and no normal germ tubes were produced. Baker et al.; Phytopathology; Vol 73, No.8 (1983)).
Kernels of corn (Zea mays) of three hybrids were coated with B. subtilis, Chaetomium globosun, or captan and planted in the field in three successive years. Stands increased 9 and 14 days after planting and at season's end for all hybrids with Chaetomium and captan treatments and for one hybrid with B. subtilis treatment. Treatments hastened attainment of an approximate 95% stand by 1-3 days depending on hybrid and treatment. Stalk rot and breakage were less with the organism and captan-coated than with non-coated Kernels. The stalk rot pathogen most frequently isolated was Fusarium roseum "Graminearum". Grain yields per treatment were higher for kernels coated with captan in all years, for those coated with C. globosum for 2 of 3 years and for those coated with B. subtilis, only 1 year, than for kernels not coated. (Kommedahl and Mew; Phytopathology 65:296-300 (1975)).
There is no prior art which teaches the use of B. subtilis for control of Brown rot on stone fruit.